/*
 * ====================================================================
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at
 * http://www.apache.org/licenses/LICENSE-2.0
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied. See the License for the
 * specific language governing permissions and limitations
 * under the License.
 * ====================================================================
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation. For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 */

package org.apache.http.client;

import java.io.IOException;

import org.apache.http.HttpHost;
import org.apache.http.HttpRequest;
import org.apache.http.HttpResponse;
import org.apache.http.client.methods.HttpUriRequest;
import org.apache.http.conn.ClientConnectionManager;
import org.apache.http.params.HttpParams;
import org.apache.http.protocol.HttpContext;

/**
 * This interface represents only the most basic contract for HTTP request
 * execution. It imposes no restrictions or particular details on the request
 * execution process and leaves the specifics of state management,
 * authentication and redirect handling up to individual implementations.
 * This should make it easier to decorate the interface with additional
 * functionality such as response content caching.
 * <p/>
 * The usual execution flow can be demonstrated by the code snippet below:
 * 
 * <PRE>
 * HttpClient httpclient = new DefaultHttpClient();
 * 
 * // Prepare a request object
 * HttpGet httpget = new HttpGet(&quot;http://www.apache.org/&quot;);
 * 
 * // Execute the request
 * HttpResponse response = httpclient.execute(httpget);
 * 
 * // Examine the response status
 * response.getStatusLine();
 * 
 * // Get hold of the response entity
 * HttpEntity entity = response.getEntity();
 * 
 * // If the response does not enclose an entity, there is no need
 * // to worry about connection release
 * if (entity != null) {
 * 	InputStream instream = entity.getContent();
 * 	try {
 * 		
 * 		BufferedReader reader = new BufferedReader(new InputStreamReader(
 * 				instream));
 * 		// do something useful with the response
 * 		reader.readLine();
 * 		
 * 	} catch (IOException ex) {
 * 		
 * 		// In case of an IOException the connection will be released
 * 		// back to the connection manager automatically
 * 		throw ex;
 * 		
 * 	} catch (RuntimeException ex) {
 * 		
 * 		// In case of an unexpected exception you may want to abort
 * 		// the HTTP request in order to shut down the underlying
 * 		// connection and release it back to the connection manager.
 * 		httpget.abort();
 * 		throw ex;
 * 		
 * 	} finally {
 * 		
 * 		// Closing the input stream will trigger connection release
 * 		instream.close();
 * 		
 * 	}
 * 	
 * 	// When HttpClient instance is no longer needed,
 * 	// shut down the connection manager to ensure
 * 	// immediate deallocation of all system resources
 * 	httpclient.getConnectionManager().shutdown();
 * }
 * </PRE>
 * 
 * @since 4.0
 */
public interface HttpClient {
	
	/**
	 * Obtains the parameters for this client.
	 * These parameters will become defaults for all requests being
	 * executed with this client, and for the parameters of
	 * dependent objects in this client.
	 * 
	 * @return the default parameters
	 */
	HttpParams getParams();
	
	/**
	 * Obtains the connection manager used by this client.
	 * 
	 * @return the connection manager
	 */
	ClientConnectionManager getConnectionManager();
	
	/**
	 * Executes a request using the default context.
	 * 
	 * @param request
	 *            the request to execute
	 * @return the response to the request. This is always a final response,
	 *         never an intermediate response with an 1xx status code.
	 *         Whether redirects or authentication challenges will be returned
	 *         or handled automatically depends on the implementation and
	 *         configuration of this client.
	 * @throws IOException
	 *             in case of a problem or the connection was aborted
	 * @throws ClientProtocolException
	 *             in case of an http protocol error
	 */
	HttpResponse execute(HttpUriRequest request) throws IOException,
			ClientProtocolException;
	
	/**
	 * Executes a request using the given context.
	 * The route to the target will be determined by the HTTP client.
	 * 
	 * @param request
	 *            the request to execute
	 * @param context
	 *            the context to use for the execution, or <code>null</code> to
	 *            use the default context
	 * @return the response to the request. This is always a final response,
	 *         never an intermediate response with an 1xx status code.
	 *         Whether redirects or authentication challenges will be returned
	 *         or handled automatically depends on the implementation and
	 *         configuration of this client.
	 * @throws IOException
	 *             in case of a problem or the connection was aborted
	 * @throws ClientProtocolException
	 *             in case of an http protocol error
	 */
	HttpResponse execute(HttpUriRequest request, HttpContext context)
			throws IOException, ClientProtocolException;
	
	/**
	 * Executes a request to the target using the default context.
	 * 
	 * @param target
	 *            the target host for the request.
	 *            Implementations may accept <code>null</code> if they can still
	 *            determine a route, for example
	 *            to a default target or by inspecting the request.
	 * @param request
	 *            the request to execute
	 * @return the response to the request. This is always a final response,
	 *         never an intermediate response with an 1xx status code.
	 *         Whether redirects or authentication challenges will be returned
	 *         or handled automatically depends on the implementation and
	 *         configuration of this client.
	 * @throws IOException
	 *             in case of a problem or the connection was aborted
	 * @throws ClientProtocolException
	 *             in case of an http protocol error
	 */
	HttpResponse execute(HttpHost target, HttpRequest request)
			throws IOException, ClientProtocolException;
	
	/**
	 * Executes a request to the target using the given context.
	 * 
	 * @param target
	 *            the target host for the request.
	 *            Implementations may accept <code>null</code> if they can still
	 *            determine a route, for example
	 *            to a default target or by inspecting the request.
	 * @param request
	 *            the request to execute
	 * @param context
	 *            the context to use for the execution, or <code>null</code> to
	 *            use the default context
	 * @return the response to the request. This is always a final response,
	 *         never an intermediate response with an 1xx status code.
	 *         Whether redirects or authentication challenges will be returned
	 *         or handled automatically depends on the implementation and
	 *         configuration of this client.
	 * @throws IOException
	 *             in case of a problem or the connection was aborted
	 * @throws ClientProtocolException
	 *             in case of an http protocol error
	 */
	HttpResponse execute(HttpHost target, HttpRequest request,
			HttpContext context) throws IOException, ClientProtocolException;
	
	/**
	 * Executes a request using the default context and processes the
	 * response using the given response handler.
	 * 
	 * @param request
	 *            the request to execute
	 * @param responseHandler
	 *            the response handler
	 * @return the response object as generated by the response handler.
	 * @throws IOException
	 *             in case of a problem or the connection was aborted
	 * @throws ClientProtocolException
	 *             in case of an http protocol error
	 */
	<T> T execute(HttpUriRequest request,
			ResponseHandler<? extends T> responseHandler) throws IOException,
			ClientProtocolException;
	
	/**
	 * Executes a request using the given context and processes the
	 * response using the given response handler.
	 * 
	 * @param request
	 *            the request to execute
	 * @param responseHandler
	 *            the response handler
	 * @return the response object as generated by the response handler.
	 * @throws IOException
	 *             in case of a problem or the connection was aborted
	 * @throws ClientProtocolException
	 *             in case of an http protocol error
	 */
	<T> T execute(HttpUriRequest request,
			ResponseHandler<? extends T> responseHandler, HttpContext context)
			throws IOException, ClientProtocolException;
	
	/**
	 * Executes a request to the target using the default context and
	 * processes the response using the given response handler.
	 * 
	 * @param target
	 *            the target host for the request.
	 *            Implementations may accept <code>null</code> if they can still
	 *            determine a route, for example
	 *            to a default target or by inspecting the request.
	 * @param request
	 *            the request to execute
	 * @param responseHandler
	 *            the response handler
	 * @return the response object as generated by the response handler.
	 * @throws IOException
	 *             in case of a problem or the connection was aborted
	 * @throws ClientProtocolException
	 *             in case of an http protocol error
	 */
	<T> T execute(HttpHost target, HttpRequest request,
			ResponseHandler<? extends T> responseHandler) throws IOException,
			ClientProtocolException;
	
	/**
	 * Executes a request to the target using the given context and
	 * processes the response using the given response handler.
	 * 
	 * @param target
	 *            the target host for the request.
	 *            Implementations may accept <code>null</code> if they can still
	 *            determine a route, for example
	 *            to a default target or by inspecting the request.
	 * @param request
	 *            the request to execute
	 * @param responseHandler
	 *            the response handler
	 * @param context
	 *            the context to use for the execution, or <code>null</code> to
	 *            use the default context
	 * @return the response object as generated by the response handler.
	 * @throws IOException
	 *             in case of a problem or the connection was aborted
	 * @throws ClientProtocolException
	 *             in case of an http protocol error
	 */
	<T> T execute(HttpHost target, HttpRequest request,
			ResponseHandler<? extends T> responseHandler, HttpContext context)
			throws IOException, ClientProtocolException;
	
}
